1. Field of the Invention
This invention relates to a new and improved process for making guar or derivatized guar slurries, or more particularly, for making non-aqueous suspensions of guar or derivatized guar. Novel aspects of the invention relate to processes for the conversion of guar splits (or derivatized guar splits) to a guar slurry suitable for use in oil and gas well stimulation treatments; the combining and/or elimination of process steps as currently practiced to provide for a more economical process as expressed by lower potential for material loss; fewer process control and quality control steps; more consistent product quality; and the elimination of potentially hazardous organic dust conditions.
2. Description of the Related Art
Guar (Cyamopsis tetragonolobus) splits are endosperm hemispheres found in the guar bean. Grown predominantly in India and Pakistan, guar beans are processed to produce guar splits. Keen et al., U.S. Pat. No. 3,132,681 incorporated in its entirety herein by reference, teaches a process for splitting and dehulling guar beans to produce guar splits. Guar splits are imported into the United States and, as such, are the “source” material from which guar powder and derivatized guar powders are manufactured for many industrial uses, including but not limited to oil well fracturing applications.
Guar and derivatized guar powders are used extensively in well fracturing applications to produce polymer solutions and crosslinked polymer solutions (i.e., gels) suitable as fracturing fluids to translate hydraulic force sufficient to initiate and propagate a fracture. The art of well fracturing to enhance the rate of production of hydrocarbons is well known to those in the industry of oil and gas production, and fracturing fluids formulated from guar and derivatized guar products are well known to those of ordinary skill in the art. The guar and derivatized guar products used in the formulation of fracturing fluids are either finely ground powders or dispersions of those same powders in non-aqueous suspensions. Non-aqueous suspensions of guar or derivatized guar powders are typically called slurries, guar slurries, or derivatized guar slurries if, in the case of the latter, the dispersed and suspended guar powder is a derivatized guar. Guar slurries are the preferred guar product in continuous mix fracturing treatments due to the ease in which the guar or derivatized guar product can be metered to form the guar or crosslinked guar fracturing fluid. Guar derivatives typically employed in well fracturing applications include hydroxyalkyl guars, carboxyalkyl guars, and carboxyalkyl hydroxyalkyl guars. Preferred guar derivatives include hydroxypropyl guars (HPG), carboxymethyl guars (CMG), and carboxymethyl hydroxypropyl guars (CMHPG).
Numerous patents relate to the manufacture of guar powder from guar splits. Exemplary are Elverum, U.S. Pat. No. 2,891,050; Keen, U.S. Pat. No. 3,455,899; Rutenberg et al., U.S. Pat. No. 4,269,975; Wu, U.S. Pat. No. 4,659,811; Yeh, et al., U.S. Pat. No. 5,489,694; Swartz, et al., U.S. Pat. No. 6,048,563; and Wieling a, U.S. Pat. No. 6,664,381. Elements from one or more of these teachings are incorporated by those of ordinary skill in the art to the manufacture of guar powder for well stimulation applications. All are incorporated herein by reference. None relate to the manufacture of guar slurries from guar splits.
Numerous patents relate to the manufacture of derivatized guar powder from guar splits. Exemplary are Moe, U.S. Pat. No. 2,496,670; Boonstra, et al., U.S. Pat. No. 3,912,713; Trapasso, U.S. Pat. No. 4,011,393; DeGuin, et al., U.S. Pat. No. 4,169,945; Bayerlein, et al., U.S. Pat. No. 4,645,833; Wu, U.S. Pat. No. 4,659,811; and Bayerlein, et al., U.S. Pat. No. 4,745,184. Others have taught methods for the derivitization of guar from guar powder. Exemplary are Nordgren, U.S. Pat. No. 3,740,389; Trapasso, U.S. Pat. No. 4,011,393; DeMartino, et al., U.S. Pat. No. 4,031,307; Tessler, U.S. Pat. No. 4,276,414; Dawson, U.S. Pat. No. 6,387,853; and Magallanes, et al., U.S. Pat. No. 6,884,884. All are incorporated herein by reference. None teach a method for the manufacture of derivatized guar slurries from guar splits.
Exemplary of teachings that relate to the manufacture of guar and derivatized guar slurries for well stimulation applications are Hostettler, et al., U.S. Pat. No. 5,091,448; Dawson, U.S. Pat. No. 6,387,853; Harris, U.S. Pat. No. 6,818,597; Magallanes, et al., U.S. Pat. No. 6,884,884; Parris, et al., U.S. Pat. No. 7,199,084; and Lin, et al., U.S. Pat. No. 7,304,019. All are incorporated herein by reference. None teach a method for the manufacture of guar or derivatized guar slurries from guar splits.
There is an overwhelming and abiding need for an efficient process for the manufacture of guar and derivatized guar slurries utilizing guar splits as the “raw” guar component.